An acre of swampland liquefied into muck the consistency of pea soup, toppling tall baldcypress trees and bending a 400-foot-long section of a natural gas pipeline toward the liquid acre.
Louisiana Highway 70, which crosses over three natural gas pipelines at the edge of the liquefied area, was closed more than 24 hours while the gas was rerouted and crews worked to empty those sections of pipe, Assumption Parish emergency preparedness director John Boudreaux said. A fourth pipeline, not so near, was also closed off and was being depressurized, he said.
Three were gradually flared off and the fourth slowly vented into the air, Sheriff Mike Waguespack said.
Boudreaux said pressure in the pipelines was low enough to avoid any chance of a rupture and explosion by 8 p.m. Sunday.
About 150 homes and several businesses in the Bayou Corne and Grand Bayou areas remain under mandatory evacuation and a shelter remains open, Boudreaux said. Residents were told to leave Friday, after the soupy area appeared overnight and quickly covered about three-quarters of an acre. It expanded again Saturday afternoon, bending a 36-inch natural gas pipeline 16 feet down and 15 feet toward the muck.
That line, owned by Crosstex Energy LP of Houston, runs parallel to a pair owned by Acadian Gas Pipeline LLC of Thibodaux, Boudreaux said. He said Florida Natural Gas owns a line farther from the “slurry hole” and was asked to depressurize it as a precaution.
A large amount of water, gas or both may be seeping upward or — if an abandoned cavern in a nearby salt dome has collapsed — the ground may be falling into it, said Adam “Ted” Bourgoyne, a retired Louisiana State University petroleum geology professor.
He said liquid could be coming up through a fault line, from a well, or from natural gas stored in caverns dissolved out in an underground mountain of salt called a salt dome.
On the other hand, he said, “That area is on the edge of an old abandoned cavern.” A crack in the salt dome could quickly spread, pulling in land that is easily eroded to start with, he said.
The 28 residents of tiny Grand Bayou had to leave their homes on Christmas 2003 and stay away for 50 days because natural gas was leaking from a salt dome storage cavern and bubbling up from the ground and into water wells. Seven old water wells were plugged and contractors drilled 32 wells to vent natural gas so it would be safe for them to return.
Boudreaux said scientists and engineers will meet Monday and probably on Wednesday at LSU to consider likely sources of the current liquefaction, and state, parish and facility owners will talk to people at a community meeting Tuesday evening in Pierre Part.
Bob Gresser, a spokesman for Houston-based Texas Brine, said Friday that employees smelled something like diesel near a plugged well tied to a salt cavern around 6:30 a.m. Friday. He said company officials did not think the smell was coming from the well, which has been out of service for two years.
The brine facility was operating normally, dissolving salt out of the Napoleonville dome, he said.
Natural gas has been bubbling up from Bayou Corne and Grand Bayou, which run below and along the side of the reported “slurry area, and from a water well in the area.
Residents have also reported tremors in the area, which has a known fault.
Federal, state and parish official have been unable so far to pin down the cause of the earthquakes or the source of the natural gas releases, despite many tests on the oil, gas and brine production facilities.